Forklift system and control method thereof

ABSTRACT

An exemplary embodiment of the present disclosure provides a forklift system. The system includes a vehicle body of a forklift; a fork configured to be vertically movable at one side of the vehicle body; a sensor unit; and a control unit. The sensor unit is configured to be disposed at a front end portion of the fork to detect an external object. The control unit is configured to control movement of the vehicle body or the position of the fork according to a detection signal generated by the sensor unit.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 15/829,365filed on Dec. 1, 2017, which claims priority to and the benefit ofKorean Patent Application No. 10-2017-0055050 filed in the KoreanIntellectual Property Office on Apr. 28, 2017, the entire contents ofeach of these applications are incorporated herein by reference.

BACKGROUND (a) Field of the Disclosure

The present disclosure relates to a forklift system and a control methodthereof that may allow a fork of the forklift to be accurately insertedinto a pallet.

(b) Description of the Related Art

Generally, a pallet for supporting freight is widely used when thefreight is transported by a forklift.

However, when the freight is transported by a forklift, an accident dueto an operation error of a forklift driver may occur. Recently, forsolving such a problem, reducing manpower, and improving productivityand the working environment, an autonomously guided vehicle has beenunder development.

However, since a conventional autonomously guided vehicle operates underan assumption that the pallet is in a set position and posture, when theposition and posture of the pallet deviate from the set position andposture, it may not operate. In addition, although a method ofidentifying characteristic information of the pallet is being developedas a working method for an autonomously guided vehicle taking intoconsideration change of the position and posture of the pallet, theremay be limitations in identifying the characteristic information of thepallet according to the environment of a workplace.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the disclosure andtherefore it may contain information that does not form the prior artthat is already known in this country to a person of ordinary skill inthe art.

SUMMARY

The present disclosure has been made in an effort to provide a forkliftsystem and a control method thereof that may allow a fork of theforklift to be accurately inserted into a center of an insertion holewhen the fork is inserted into the insertion hole of the pallet.

An exemplary embodiment of the present disclosure provides a forkliftsystem including: a fork configured to be vertically movable at one sideof the vehicle body; a sensor unit configured to be disposed at a frontend portion of the fork to detect an external object; and a control unitconfigured to control movement of the vehicle body or a position of thefork according to a detection signal generated by the sensor unit.

The sensor unit may include: a sensor body configured to be fixed to thefront end portion of the fork; a contact sensor configured to contact afront object and provided at the sensor body to detect an externalobject; and a non-contact sensor configured to be provided at the sensorbody and to emit a signal upon detecting an external object.

The contact sensor may include: a contact portion configured to contactthe external object; and a contact sensor configured to be connected tothe contact portion.

The forklift system may further include an elastic member configured tobe interposed between the contact portion and the contact sensor.

The non-contact sensor may be a photosensor that detects a front objectthrough a detection path formed in the contact portion.

The contact portion may include a left contact portion and a rightcontact portion that are respectively formed at left and right sides ofthe sensor unit with respect to a center of the fork, and the contactsensor may include a left contact sensor corresponding to the leftcontact portion and a right contact sensor corresponding to the rightcontact portion.

The control unit may move the vehicle body backward when the non-contactsensor emits a signal upon detecting an external object.

The control portion may rotate the vehicle body rightward by apredetermined angle when the left contact portion of the contact sensorgenerates a signal.

The control portion may rotate the vehicle body leftward by apredetermined angle when the right contact portion of the contact sensorgenerates a signal.

The forklift system may further include: a navigation sensor configuredto be provided at one side of the vehicle body to detect a position ofthe vehicle body; and a laser sensor configured to be disposed between apair of forks to detect a position of the pallet to which the forks arefastened.

Another embodiment of the present disclosure provides a fork sensor unitdisposed at a front end portion of a fork for detecting an externalobject, the fork sensor unit including: a sensor body configured to befixed to the front end portion of the fork; a contact sensor configuredto contact a front object and provided at the sensor body to detect anexternal object; and a non-contact sensor configured to be provided atthe sensor body and to emit light to the outside upon detecting anexternal object.

The contact sensor may further include a contact portion configured tocontact the external object; and a contact sensor configured to beconnected to the contact portion.

The fork sensor unit may further include an elastic member configured tobe interposed between the contact portion and the contact sensor.

The non-contact sensor may be a photosensor that detects a front objectby using a wavelength emitted in front of the fork through a detectionpath formed in the contact portion.

The contact portion may include left and right contact portionsrespectively formed at left and right sides with respect to a center ofthe fork. The contact sensor may include left and right contact sensorscorresponding to the left and right contact portions, respectively.

Yet another embodiment of the present disclosure provides a controlmethod of a forklift, the forklift having two forks, the methodincluding: detecting a shape of and a distance to a target pallet byusing a laser sensor; approaching a vehicle body to the pallet;detecting an angle (θ) between a pallet center line of the pallet and avehicle body center line of the vehicle body; and controlling a positionof the vehicle body so that the angle (θ) is within a predeterminednumerical value.

The control method of the forklift may further include: detecting anangle (θ′) between a front surface line of the pallet and a front endline of the fork; and controlling a position of the vehicle body so thatthe angle (θ′) is within a predetermined numerical value.

The control method of the forklift may further include: measuring adistance between fork insertion holes formed in the pallet by using thelaser the laser sensor; and adjusting a distance between the forksaccording to the distance between the fork insertion holes.

The control method of the forklift may further include moving thevehicle body so that the forks are inserted into the fork insertionholes formed in the pallet.

The control method of the forklift may further include detecting asignal generated by a sensor unit provided at a front end of the fork ofthe forklift; and controlling movement of the forklift by using thesignal.

The control method of the forklift may further include, when anon-contact sensor provided at the sensor unit generates a signal upondetecting an external object, the vehicle body is moved backward, andwhen a contact sensor provided at the sensor unit generates a signalupon contacting a front object to detect an external object, the vehiclebody is rotated rightward or leftward by a predetermined angle.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates a top plan view of an autonomously guided forkliftincluding a fork sensor unit according to an exemplary embodiment of thepresent disclosure.

FIG. 2 illustrates a top plan view of the inside of a fork sensor unitaccording to an exemplary embodiment of the present disclosure.

FIG. 3 illustrates a front view of a fork sensor unit according to anexemplary embodiment of the present disclosure.

FIG. 4 illustrates a flowchart of a method executed by a control systemof an autonomously guided forklift including a fork sensor unitaccording to an exemplary embodiment of the present disclosure.

FIG. 5 illustrates a schematic view of a control system of anautonomously guided forklift including a fork sensor unit according toan exemplary embodiment of the present disclosure.

FIG. 6 is a schematic top plan view for showing control factors betweenan autonomously guided forklift and a pallet according to an exemplaryembodiment of the present disclosure.

FIG. 7 illustrates a flowchart of a control method of an autonomouslyguided forklift according to an exemplary embodiment of the presentdisclosure.

DETAILED DESCRIPTION

Hereinafter, an exemplary embodiment of the present disclosure will bedescribed in detail with reference to the accompanying drawings.

FIG. 1 illustrates a top plan view of an autonomously guided forkliftincluding a fork sensor unit according to an exemplary embodiment of thepresent disclosure.

Referring to FIG. 1, an autonomously guided forklift 100 includes avehicle body 105, a vertical moving member 122, a fork 120, a navigationsensor 110, a laser sensor 135, and a sensor unit 130.

The navigation sensor 110 is disposed at one upper side of the vehiclebody 105 and detects a position of the autonomously guided forklift 100.

The vertical moving member 122 is disposed in front of the vehicle body105, and a pair of forks 120 is horizontally disposed in front of thevertical moving member 122. The sensor unit 130 is provided at a frontend of each of the forks 120.

The laser sensor 135 is disposed at the vertical moving member 122between the forks 120, and it may detect a shape and a position of anobject such as a front of a pallet.

Referring to FIG. 2, a detailed structure of the fork sensor unit 130will be described.

FIG. 2 illustrates a top plan view of the inside of a fork sensor unitaccording to an exemplary embodiment of the present disclosure.

Referring to FIG. 2, the sensor unit 130 includes, as constituentelements, a left contact portion 200, a left contact surface 210, adetection path 220, a right contact surface 215, a right contact portion205, an elastic member 225, a connection rod 230, a right contact sensor240, a sensor body 250, a photosensor 260, a supporting member 270, asensor bracket 280, and a left contact sensor 235.

The sensor bracket 280 is fixed to a rear end of the sensor body 250,and the sensor body 250 is mounted on a front end portion of the fork120 through the sensor bracket 280.

The supporting member 270 is fixed in front of the sensor bracket 280,and the left contact sensor 235 and the right contact sensor 240 aredisposed in front of the supporting member 270. The left contact sensor235 and the right contact sensor 240 are supported by the supportingmember 270.

The left contact portion 200 is disposed in front of the left contactsensor 235, the connection rod 230 is disposed between the left contactsensor 235 and the left contact portion 200, and the elastic member 225is disposed along the connection rod 230.

When the left contact portion 200 comes into contact with an obstacle ora pallet, the elastic member 225 is compressed and the compression forceis transmitted to the left contact sensor 235 through the connection rod230.

The right contact portion 205 is disposed in front of the right contactsensor 240, the connection rod 230 is disposed between the right contactsensor 240 and the right contact portion 205, and the elastic member 225is disposed along the connection rod 230. The elastic member 225 is atype of coil spring, and the connection rod 230 passes through a centerof the coil spring.

When the right contact portion 205 comes into contact with an obstacleor a pallet, the elastic member 225 is compressed and the compressionforce is transmitted to the right contact sensor 240.

An inclined right contact surface 215 is formed at an edge of the rightcontact portion 205, and an inclined left contact surface 210 is formedat an edge of the left contact portion 200.

FIG. 3 illustrates a front view of a fork sensor unit 130 according toan exemplary embodiment of the present disclosure.

Referring to FIG. 3, the detection path 220 is formed in front of thephotosensor 260 through the left contact portion 200 and the rightcontact portion 205, which are disposed in front of the photosensor 260.In addition, the photosensor 260 is disposed between the left contactsensor 235 and the right contact sensor 240, and the photosensor 260photographs a front thereof through the detection path 220.

FIG. 4 illustrates a flowchart of a method executed by a control systemof an autonomously guided forklift including a fork sensor unitaccording to an exemplary embodiment of the present disclosure.

Referring to FIG. 4, docking retry logic starts at step S400. Here, thedocking may mean that the fork 120 enters into a fork insertion hole(not shown) of the pallet (not shown), and the docking retry logic maybe logic to attempt insertion of the fork 120 into the fork insertionhole of the pallet.

When the photosensor 260 of the fork 120 generates a sensing signal(S405), a control unit 500 moves the vehicle body 105 right backward(S420). When the photosensor 260 of the fork 120 does not generate asensing signal (S435), step S460 is performed. The docking retry logicis ended at step S460.

When the left contact sensor 235 and the right contact sensor 240 of thefork 120 generate detection signals (S410), the control unit 500 movesthe vehicle body 105 right backward (S425). When the left contact sensor235 and the right contact sensor 240 of the fork 120 do not generatedetection signals (S440), step S460 is performed.

When the left contact sensor 235 or the right contact sensor 240 of thefork 120 generates a detection signal (S415), the control unit 500rotates the vehicle body 105 in a right or left direction (S430). Whenthe left contact sensor 235 and the right contact sensor 240 of the fork120 do not generate a detection signal (S450), step S460 is performed.

FIG. 5 illustrates a schematic view of a control system of anautonomously guided forklift including a fork sensor unit according toan exemplary embodiment of the present disclosure.

Referring to FIG. 5, a control system of an autonomously guided forkliftincludes the control unit 500, a drive unit 510, and a sensing unit 520,and the drive unit 510 includes a steering drive unit 530, a fork driveunit 540, and a traveling drive unit 550.

The steering drive unit 530 may control a moving direction and rotationof the vehicle body 105, and the fork drive unit 540 may control adistance between, and vertical heights and longitudinal angles of, theforks 120. Herein, since a steering device, a fork operating device, anda drive device are well known in the art, a detailed description thereofwill be omitted.

The control unit 500 may be implemented by one or more processorsoperated by a predetermined program, and the predetermined program mayinclude a series of commands for performing a method according to anexemplary embodiment of the present disclosure.

The sensing unit 520 includes the navigation sensor 110, the lasersensor 135, and the sensor unit 130, and the control unit 500 maycontrol constituent elements of the drive unit 510 by using signalssensed by constituent elements of the sensing unit 520.

In the exemplary embodiment of the present disclosure, the photosensormay be a non-contact sensor that may emit light forward or photograph aforward object, and the left contact sensor and the right contact sensormay be contact sensors.

FIG. 6 is a schematic top plan view for showing control factors betweenan autonomously guided forklift and a pallet according to an exemplaryembodiment of the present disclosure. While comparing with the exemplaryembodiments of FIGS. 1 to 5, characteristic differences will bedescribed.

Referring to FIG. 6, a fork front end connecting line 605 connecting afront end of the fork 120 is shown, and a pallet front surface line 615is shown along a front surface of a pallet 600.

The control unit 500 detects an angle (θ′) formed between the lines 605and 615, and it may control movement of the vehicle body 105 so that theangle is included within a predetermined set value.

In addition, a pallet center line 635 of the pallet 600 and a vehiclebody center line 640 of the autonomously guided forklift 100 are shown.

The control unit 500 detects an angle (θ) formed between the palletcenter line 635 and the vehicle body center line 640, and it may controlmovement of the vehicle body 105 so that the angle is included within apredetermined set value.

The control unit 500 may detect a distance 610 and a shape of the pallet600 positioned in front thereof through the laser sensor 135, maycontrol movement of the vehicle body 105 in approaching the pallet 600,and then may control movements of the vehicle body 105 and the fork 120so that the fork 120 may be inserted into a fork insertion hole 620formed in the pallet 600.

FIG. 7 illustrates a flowchart of a control method of an autonomouslyguided forklift according to an exemplary embodiment of the presentdisclosure.

Referring to FIG. 7, a target pallet 600 in front of the autonomouslyguided forklift in a traveling state is searched by using the lasersensor 135 (S300). In addition, the movement of the vehicle body 105 iscontrolled in approaching the target pallet 600 (S310).

The angle (θ) between the pallet center line 635 passing through thecenter of the pallet 600 and the vehicle body center line 640 of theforklift is detected (S320). In addition, the movement of the vehiclebody 105 is controlled and if need be corrected so that the angle (θ)may be included within a predetermined set value (S330).

The vehicle body 105 is brought closer to the pallet 600 (S340). Theangle (θ′) between the pallet front surface line 615 shown along thefront surface of the pallet 600 and the fork front end line 605connecting the front end of the fork 120 of the forklift is detected(S350). In addition, the movement of the vehicle body 105 is controlledand if need be corrected so that the angle (θ′) may be included within apredetermined set value (S360).

The laser sensor 135 measures a distance 630 between the fork insertionholes 620 formed in the pallet 600 (S370). In addition, the control unit500 adjusts an interval of the forks 120 of the forklift (distancebetween the forks in the drawing) (S380).

The control unit 500 moves the vehicle body 105 to perform docking sothat each fork 120 is inserted into a fork insertion hole 620 of thepallet 600 (S390).

In the exemplary embodiment of the present disclosure, while the dockingis performed at step S390, as described in FIG. 4, the docking retrylogic may be performed. In this case, the sensor unit 130 provided atthe front end of the fork 120 operates. As shown in FIG. 4, the controlunit 500 may control the movement of the vehicle body 105 of theforklift according to the detected signal.

According to the exemplary embodiment of the present disclosure, when afront object is detected by the non-contact sensor of the fork sensorunit 130, it is possible to improve docking accuracy between the palletand the fork by moving the vehicle backward. In addition, by rotatingthe vehicle body in a right direction when a signal from the leftcontact sensor is detected and by rotating the vehicle body in a leftdirection when a signal from the right contact sensor is detected, it ispossible to easily insert the fork into the center of the insertion holeof the pallet, thereby improving docking accuracy. Further, by using thecontact sensor and the non-contact sensor, it is possible to allow thefork to effectively detect an obstacle, thereby improving the dockingaccuracy between the fork and the pallet.

While this disclosure has been described in connection with what ispresently considered to be practical exemplary embodiments, it is to beunderstood that the disclosure is not limited to the disclosedembodiments. On the contrary, it is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

The invention claimed is:
 1. A control method of a forklift, theforklift having two forks, the method comprising: detecting a shape ofand a distance to a target pallet by using a laser sensor; approaching avehicle body to the pallet; detecting an angle (θ) between a palletcenter line of the pallet and a vehicle body center line of the vehiclebody; controlling a position of the vehicle body so that the angle (θ)is within a predetermined numerical value; detecting a signal generatedby a sensor unit provided at a front end of the fork of the forklift;and controlling movement of the forklift by using the signal; whereinwhen a non-contact sensor provided at the sensor unit generates a signalupon detecting an external object, the vehicle body is moved backward;and when a contact sensor provided at the sensor unit generates a signalupon contacting a front object to detect an external object, the vehiclebody is rotated rightward or leftward by a predetermined angle.
 2. Thecontrol method of the forklift of claim 1, further comprising: detectingan angle (θ′) between a front surface line of the pallet and a front endline of the fork; and controlling a position of the vehicle body so thatthe angle (θ′) is within a predetermined numerical value.
 3. The controlmethod of the forklift of claim 1, further comprising: measuring adistance between fork insertion holes formed in the pallet by using thelaser sensor; and adjusting a distance between the forks according tothe distance between the fork insertion holes.
 4. The control method ofthe forklift of claim 2, further comprising: moving the vehicle body sothat the forks are inserted into the fork insertion holes formed in thepallet.